code: def test_colormap_single_hue():
      """Test colormap support using a single hue()"""
      from vispy.color.colormap import SingleHue
  
      with TestingCanvas(size=size, bgcolor="w") as c:
          idata = np.linspace(255, 0, size[0] * size[1]).astype(
              np.ubyte
          )
          data = idata.reshape((size[0], size[1]))
          cmap = SingleHue(255)
          image = Image(cmap=cmap, clim="auto", parent=c.scene)
          image.set_data(data)
          assert_image_approved(c.render(), "visuals/colormap_hue.png")
  
file_path: vispy/vispy/visuals/tests/test_colormap.py
imports: import numpy
  from vispy.scene.visuals import Image
  from vispy.testing import requires_application, TestingCanvas, run_tests_if_main
  from vispy.testing.image_tester import assert_image_approved
  from vispy.color import Colormap
label_desc: Use image node_id 4 for calling a global function with example usage: test_colormap_single_hue() without return types